US Preliminary Extended Weather thru Mar 23

Overview...

The Upper Pattern Will Be Driven By The Two Robust Positive Height
Anomalies In The North Atlantic And Over The North Pole That Should Merge Over Northern Greenland/Canadian Islands Over The Next Week.

End Result In This Very Negative Ao Pattern Is Broad East Coast Troughing With Ridging Attempting To Build Into The Sw States.

...Model Preferences...

The Global Ensembles Show Good Agreement On The Expected Synoptic Pattern While Their Deterministic Counterparts Become Less Agreeable In Time.

A Compromise Between The 18z Gfs And 12z Ecmwf Fared Well For The First Half Of The Forecast Period With The Exiting System In The Northeast And Even The Rather Poorly Handled System Approaching The West Coast /Continuity Has Been Less Than Desired Here But A Blend Seems To Converge Toward The Ecmwf Ensemble Mean/.

The Most Changeable Part Of The Forecast Remains Fri-Sat/D6-7.

The Ecmwf And Its Mean Have Showed A Much More Suppressed System Moving Out Of The Rockies And Through The Southern Plains Toward The Southeast States Compared To The Gfs.

The Gefs Ensembles Fall Somewhat In Between But Have Trended Toward The Ecmwf Idea In Recent Runs.

Though The Gfs Has Shifted Its Focus For Low Pressure Through The Southeast Rather Than Through The Midwest/Oh Valley It Has Yet To Completely Abandon It.

Given The Upper Low In Place Over Quebec... This Energy Should Be Forced Eastward Rather Than Northeastward But Kept A Small Weighting Of The 18z Gfs Throughout The Forecast As It Does Shift Its Energy Off The Nc Coast Like The Ecmwf... But At A Pace More Consistent With The Ensembles.

...Sensible Weather Highlights...

Exiting System In The Northeast At The Start Of The Period Will Keep Lake Effect Favored Areas Cold And Unsettled With Light Snow
Diminishing In Coverage Over A Few Days.

Cold High Pressure Through The Central Plains Will Keep Temperatures Well Below Normal East Of The Rockies And North Of About 30n.

Florida Should Mostly Escape The Cold Push As The Frontal Boundary Gets Hung Up On Wed/D4 Before Pushing Back Northward.

In The West... Sfc System Associated With A Vigorous Closed Low
Ejecting From Near Hawaii In The Short Term Should Find Its Way
Toward Vancouver Island /Much Farther North Than What Was Forecast 24 Hrs Ago/ Though There Is Still A Fair Amount Of Ensemble Spread.

Frontal Boundary Should Spread Modest Qpf Through The West
/Except The Sw Deserts/ Midweek Before Translating Eastward By The End Of The Week.

Precip Focus Should Stay South Of About 35n With Low Pressure Exiting The Coast Off Nc/Sc But Gulf Moisture Should Be Available Especially Along And North Of The Frontal Boundary For At Least An Inch Or Two Of Rain Over Much Of The Southeast Days 6-7.


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